Fluid processing apparatus typically utilize one or more kinds of fluid processing media to process fluid such as water or aqueous solutions, and typically comprise one or more fluid processing units containing the fluid processing media. When fluid passes through the fluid processing media, impurities and/or contaminants therein are separated from the fluid by physical and/or chemical reaction with the processing media. A typical example of such fluid processing apparatus is the tap water purifying and softening apparatus. Such water processing apparatus provide families with purified water suitable for direct drinking and washing water, and at present are already important appliances for family use, especially for Chinese families.
For a long time, the softening apparatus has been basically the only means for processing hard water, and some other alternative means such as magnetic devices, electromagnetic devices, RF devices and catalysts have not been proved effective. The template-assisted crystallization (TAC) technology emerging in recent years is a very effective fluid processing medium, which uses special polymer particles as the fluid processing medium to allow hard water minerals (for example, CaCO3) in water to precipitate and adhere onto the surface of the polymer particles in the form of harmless, inactive crystalline micro-particles, which grow to a certain size and are then released from the polymer particles to water and suspended in water in the form of non-reactive, non-adhesive grains, so as to effectively prevent formation of scale. Thus, unlike conventional fluid processing systems, TAC-based fluid processing systems do not entrap hard water minerals, but only turn hard water minerals into the form of grains.
An example of the fluid processing system using the TAC technology is the system using Next-ScaleStop as the fluid processing medium; according to the international regulations of scale prevention, the Next-ScaleStop fluid processing medium is up to 96% efficient, more efficient than any other water softener. Next-ScaleStop has the following advantages: (1) it does not require use of any chemicals, and therefore is more environmentally friendly; (2) it provides protection against scale for a whole house; (3) the medium has a long life, and is not consumed by the reaction; and (4) it retains beneficial minerals in water; (5) it brings no slimy feeling as soft water has. The Next-ScaleStop fluid processing medium is of polymer particles having a size of 0.55 to 0.85 mm (about 20×40 mesh) and a bulk density of about 0.67 kg/l.
On the surface of the polymer particles (or polymer beads) (such as Next-ScaleStop) used for the TAC-based water softening technology, there are a lot of nucleation sites of an atomic size, and at these sites dissolved hard water material is converted into tiny “crystal seeds”. Once the crystal seeds are produced and grow to a certain size, the water flowing through the template-assisted crystallization (TAC) fluid processing medium contained in the column bed units will take them off the surface of the polymer particles. Thus, the mechanism of the TAC-based water softening technology is generally described as follows: (1) the dissolved hard water material is converted into tiny “crystal seeds” on the surface of polymer particles having many nucleation sites; (2) it takes several hours for the crystal seeds to grow by 10%, thus, if the flow of water is stopped throughout the night, the size of the crystal seeds released from the TAC column bed will be only slightly larger than that of normal crystal seeds; so, after the water flows for a few minutes, at various flow rates, the size of the crystal seeds released from the particle surface of a TAC column bed will again become normal (variation within only 10% or less); (3) newly produced crystal seeds adhere to the nucleation sites of an atomic size and grow, until they are flushed into the water flow, and the release rate of crystal seeds is proportional to the flow rate of water. Therefore, in order to improve the performance of TAC, a general solution is to maximize the flow rate of the water, i.e., to change from a low flow rate to a high flow rate.
Regarding the fixed column bed of a TAC-based water softening apparatus, it has the following characteristics:
1) When the flow speed is low, the kinetic energy of water molecules is low, and the “crystal seeds” flushed off the nucleation sites of an atomic size would be less. Thus, the free nucleation sites for formation of new crystal seeds will decrease, so that new crystal seeds are produced at a low rate.
2) When the flow speed is high, the kinetic energy of water molecules is high, and more “crystal seeds” would be flushed off the nucleation sites of an atomic size. Thus, the free nucleation sites for formation of new crystal seeds will increase, so that new crystal seeds are produced at a high rate.
Thus, for the TAC-based water processing system, provided that the depth of the column bed and the cross-sectional area for filtration are fixed, the lower the water flow speed is, the “crystal seeds” would be released to the water flow at a lower rate; the higher the water flow speed is, the “crystal seeds” would be released to the water flow at a higher rate. For the conventional filtration function, provided that the depth of column bed and the cross-sectional area for filtration are fixed, the lower the water flow speed is, the higher the filtration efficiency is. That is, in this regard, TAC is contrary to conventional filtration. In general, the mechanism of conventional filtration is that more adsorption leads to higher efficiency, while the mechanism of the TAC system is that less adsorption leads to higher efficiency. Current Next-ScaleStop fluid processing apparatus use only one column bed unit. When the flow rate of water is low, the flow speed of water passing through the column bed unit is low, resulting in a poor crystallization effect.
The present inventor has paid attention to this feature of the TAC technology and developed a method for improving the performance of a TAC-based water processing system.
Although the background of invention is described above, not all of the above contents are necessarily in the prior art.